1. Field of the Invention
The disclosures herein generally relate to a communication system.
2. Description of the Related Art
Various position information management systems have been proposed for determining positions of a person or an object that has a wireless terminal in facilities indoors where accurate positioning with GPS or the like is difficult.
Japanese Patent No. 4620410 (referred to as Patent document 1 hereafter) discloses a system in which a passive RF tag attached to a person is read by a fixed RF reader/writer, with which the position of the person is indicated to other wireless terminals or the like.
Japanese Laid-open Patent Application No. 2010-159980 (referred to as Patent document 2 hereafter) discloses a system in which a wireless terminal identifies its own position by converting an identifier sent from a nearby transmitter into position identification information.
WO 2005/086375 (referred to as Patent document 3 hereafter) discloses a system in which a wireless terminal receives intrinsic information from an illuminator, which is sent to a server to identify the position of the wireless terminal.
However, the system in Patent document 1 may increase the initial cost for installing the infrastructure because a number of RF reader/writers may need to be installed for reading passive RF tags whose communication ranges are limited.
Also, the system in Patent document 2 may have considerable power consumption depending on a communication method between a wireless terminal and a server.
Moreover, the system in Patent document 3 does not take power consumption into account as in the system in Patent document 2. It may have a higher computation cost at the server to search for positions associated with the intrinsic information to identify the positions of the wireless terminals.